The present invention generally relates to a reheating furnace and more particularly, to a walking beam type reheating furnace wherein hot or cold steel workpieces such as slabs, blooms, billets or the like can be heated not only separately, but also in a state where they are mixed together with each other.
The walking beam type reheating furnace generally has functions of transferring the workpieces which have been bloomed or have been discharged from a continuous casting machine towards a discharge side of the furnace in steps by being displaced on stationary beams and on movable beams alternately through repeating rectangular motions of the movable beams which are disposed in a longitudinal direction of the furnace, while the workpieces are heated up to a target temperature by burners and thereafter, they are transferred from a discharge port of the furnace towards a hot rolling machine for an after-process thereon.
Meanwhile, it is desirable, from the viewpoint of saving energy, to charge the workpieces into the furnace from a charge port defined at an intermediate portion thereof in the case of hot workpieces or from another charge port defined at the charge end portion thereof in the case of cold workpieces.
One type of continuous reheating furnace for conducting the above described heating process is disclosed in, for example, Japanese Patent Laid-Open Publication Tokkaisho No. 58-104114, wherein a walking hearth type transfer means is employed for transferring the workpieces and there is an opening in a side wall at the intermediate portion of the furnace for charging the hot workpieces therethrough. Furthermore, each of the hot workpieces is charged into the furnace by a pusher located outside the furnace and is subsequently heated up, while being transferred towards a discharge side of the furnace in steps through the rectangular motions of the walking hearth. In this kind of reheating furnace, however, the fact that the hot workpieces are charged into the furnace by the pusher undesirably results in trouble with respect to the transfer of the workpieces in that not only are they damaged at the lower surface thereof by getting in contact with the upper surface of the hearth, but also they are charged out of position in the furnace or they are obliquely transferred therein.
Moreover, it is necessary to provide such a charging line for exclusive use as a hot workpiece charging device in addition to a cold workpiece charging one and as a result, the installation space required therefor tends to be large with an increasing cost of equipment.
On the other hand, another type of continuous reheating furnaces is disclosed in, for example, Japanese Patent Laid-Open Publication Tokkaisho No. 55-134125, wherein a walking beam type transfer means is employed for transferring the workpieces and there is an opening in a top wall at the intermediate portion of the furnace for charging the hot workpieces therethrough. Each of the hot workpieces is charged into the furnace by being hung down by a fork device or the like disposed above the opening and is subsequently heated up, while being transferred towards a discharge side of the furnace in steps through the rectangular motions of the walking beams. In this kind of reheating furnace, although the hot workpieces can be freed from the damage at the lower surface thereof due to the fact that they are not charged into the furnace by the pusher, there has been some problem related to security of safety or efficient workability since not only is a seal device for sealing the opening or a hanging device for hanging down the hot workpiece arranged on the furnace inevitably on a large scale, but also the atmosphere which is high in temperature spouts from the opening at the time when the hot workpiece is charged.
In addition, either type of the aforementioned reheating furnaces does not have sufficient functions for coping with a variety of treatments for the workpieces.